近平衡压力固井技术在超深易漏失井的应用

五探1井是部署在四川盆地川东地区下古生界—震旦系勘探新领域的一口重点风险探井，完钻井深8 060 m。该井六开采用?190.5 mm钻头从6 600 m钻进至7 288 m，高台组—灯影组顶，下?168.3 mm尾管固井封隔5 180~7 288 m井段，钻井过程中高台组、龙王庙组、沧浪铺组均发生过井漏，地层承压能力仅1.65 g/cm3，套管重合段环空间隙仅12.69 mm，环空摩阻大，给?168.3 mm尾管固井带来了巨大挑战。通过优选3M空心玻璃微珠、高温增强材料DRB-2S等关键材料，形成1.57 g/cm3低密度高强度韧性防窜水泥浆体系，优化浆柱结构与施工排量，使井筒薄弱点处(7 016.3 m)最大动态当量密度不超过该处地层承压能力，实现近平衡压力条件下一次性上返固井。应用结果表明:五探1井?168.3 mm尾管固井质量好，试压合格，该方法能够提高超深易漏井段的尾管固井质量，有利于改善后期高压气井试油安全作业的井筒条件，为类似易漏失井固井提供了良好的经验借鉴。

Application of the near equilibrium pressure cementing technique in ultra deep leakage wells: A case study on the ?168.3 mm liner cementing of Well Wutan 1

Well Wutan 1 is an important wildcat well deployed in the new exploration area of Lower Paleozoic-Sinian in the eastern Sichuan Basin and its total depth is 8 060 m. In the sixth section of this well, ?190.5 mm bit is used for drilling from 6 600 m to 7 288 m and ?168.3 mm liner cementing is performed in Gaotai Formation-top of Dengying Formation to isolate the interval of 5 180?7 288 m. In the process of drilling, mud loss happens in Gaotai Formation, Longwangmiao Formation and Canglangpu Formation. The formation’s pressure bearing capacity is only 1.65 g/cm3, the annulus clearance in the overlapped casing section is only 12.69 mm, and friction in the annulus is high, which brings huge challenges to the ?168.3 mm liner cementing. The anti-channeling toughness slurry system of low density (1.57 g/cm3) and high strength was prepared by optimizing the key materials, such as 3M hollow glass bead and high-temperature reinforcement material DRB-2S, and slurry column structure and construction displacement were optimized to ensure the maximum dynamic equivalent density at the weak point of the wellbore (7 016.3 m) not higher than the formation’s pressure bearing capacity at that point, so as to realize the one-trip upward cementing under the near equilibrium pressure. The application results show that the ?168.3 mm liner cementing in Well Wutan 1 is of high quality with qualified pressure test result. It is indicated that this method can improve the quality of the liner cementing in the ultra deep thief sections and is beneficial to improve the wellbore conditions for the safe well test of high-pressure gas wells. The research results provide the valuable reference for the cementing of similar leakage wells.